3 years for a man to get to and from Mars?

"Doctor Bombay" wrote in
:

Just was reading on the space dot com website that it will be a three
year mission when and if we send men to Mars.

But when I was watching the animation of the Spirit and Opportunity
missions it said it took 7 months for the rover to get to Mars.

Assuming that the Astronauts spend 2 weeks on Mars That is still only
14-1/2 months round trip.

Why will it take so much longer for men to get to Mars then Machines?

One, the MER rovers weren't pushing the capabilities of the rockets that
sent them to Mars. So it was possible to use a slightly faster trajectory
than the 258 days that a classical Hohmann transfer would provide. A human
mission would be much more massive, so providing that same level of margin
would be more expensive.

Two, the robots don't have to return. The humans must wait until the
planets are aligned properly for the return trip. That won't happen in two
weeks. Generally, the first opportunity is in about 90 days, but requires
an indirect trajectory that takes longer than a Hohmann transfer. A direct
return requires a longer surface stay, up to one year.


--
JRF

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Just was reading on the space dot com website that it will be a three
year mission when and if we send men to Mars.

But when I was watching the animation of the Spirit and Opportunity
missions it said it took 7 months for the rover to get to Mars.

Assuming that the Astronauts spend 2 weeks on Mars That is still only
14-1/2 months round trip.

Why will it take so much longer for men to get to Mars then Machines?

One, the MER rovers weren't pushing the capabilities of the rockets that
sent them to Mars. So it was possible to use a slightly faster trajectory
than the 258 days that a classical Hohmann transfer would provide. A human
mission would be much more massive, so providing that same level of margin
would be more expensive.

Two, the robots don't have to return. The humans must wait until the
planets are aligned properly for the return trip. That won't happen in two
weeks. Generally, the first opportunity is in about 90 days, but requires
an indirect trajectory that takes longer than a Hohmann transfer. A direct
return requires a longer surface stay, up to one year.

Ah I see. They need to spend more time on the surface of Mars so the planets
will bi in the proper orbit .

That make sense. THANKS!!!

BTW what does that word "Hohmann" mean? Is it an acronym?

"Doctor Bombay" writes:
Ah I see. They need to spend more time on the surface of Mars so the planets
will bi in the proper orbit .

That make sense. THANKS!!!

BTW what does that word "Hohmann" mean? Is it an acronym?

Named after the guy that discovered it, a Hohmann transfer orbit is
the most efficient (lowest fuel consumption) orbit moving from one
circular orbit to another.

To be technical, a Hohmann orbit is an ellipse with periapsis at
the smaller radius and apoapsis at the larger radius... so to actually
use it you have to wait until the planets are in the right positions,
which happens every two years or so, and they aren't symettric
(i.e.when the planets are set right to send a probe to Mars, you'll
have to wait even longer once the probe is there for the right
alignment to get back).

There are many other transfer orbits you can do, but they all
require more fuel.


--
Richard W Kaszeta

http://www.kaszeta.org/rich

Richard Kaszeta wrote:
"Doctor Bombay" writes:
Ah I see. They need to spend more time on the surface of Mars so the planets
will bi in the proper orbit .

That make sense. THANKS!!!

BTW what does that word "Hohmann" mean? Is it an acronym?

Named after the guy that discovered it, a Hohmann transfer orbit is
the most efficient (lowest fuel consumption) orbit moving from one
circular orbit to another.
snip
There are many other transfer orbits you can do, but they all
require more fuel.

Unless there are other bodies to interact with, in which case maybe not.

Unless there are other bodies to interact with, in which case maybe not.

Well the whole purpose of that nuclear booster stage was to cut transit time to
2 or 3 months each way? I dont think a 3 year trip is a viable idea. Beyond
which they should build a sooped up emergency supply vehicle for have to have
stuff that could cut that time even futher. It would need radiation shielding
for the crew so it could be light weight too. for faster journeys